Movements for such watches are themselves known. For example, patent CH 57805 described a double face pocket watch which indicates on each of its faces a different time by means of a movement including two opposed displays, the hands of which pivot around an axis passing through the center of the watch. The hands of one of the displays opposite one of the faces of the movement are set in rotation in a known manner by a minutes arbor loosely adjusted in the arbor of the center wheel, also called minutes wheel, while the hands of the other display are driven in the opposite sense by a wheel train coming into mesh with an intermediate pinion fixed opposite the other face of the movement on the same minutes arbor. The presence of the intermediate pinion arranged between the other face of the movement and the hands of the other display increases accordingly the total thickness of the caliber while introducing additional play in the motion of the hands. If that is acceptable in the case of a pocket watch, such an increase in thickness would constitute, on the other hand, an important drawback in the providing of a wrist watch in which the thickness assumes great importance from the design viewpoint. Another disadvantage of such movement comes from the fact that the displays cannot be separably set., but only together and in synchronism.
Another movement with two opposed displays has been exposed in patent application EP 0504623. In this creation, the hands of one of the displays are the hands of a known type display driven in a known manner by a dial train from the minutes arbor. The hands of the other display are set in rotation in the sense opposite to that of the first mentioned hands by a gear train arranged to be flat on the other face of the movement, in a manner to reduce as much as possible the overthickness. The transmission of the rotational movement of a wheel set of the dial train to the wheel sets arranged on the other face is obtained by means of an indented traversing cannon joining the two faces of the movement and cooperating with an exterior control push piece. If this arrangement of the wheel sets enables obtaining a movement of small thickness, on the other hand the length of the gear train introduces still more substantial play than in the preceding case in driving the hands of the other display during the synchronous time setting of the two displays. In order to render such play acceptable, the toothed wheels must exhibit small backlash and thus respond to severe manufacturing standards bringing about a high cost of manufacture. The separate setting of each display is possible in this arrangement, but this thanks to the control push piece, the presence of which complicates the design of the movement as well as that of the watch case.
The two arrangements which have just been described which concern mechanical as well as electronic analog movements thus present substantial drawbacks which the present invention, on the other hand applicable only to mechanical movements with a sprung balance, proposes to overcome.